See the manual for grub2 (i presume you are not really running grub anymore) and runlevels. I think in your case starting to runlevel 2 might help as it doesn't start the network (obviously this will not start a graphical environment as 3 does).

_________________MfG. DonKult
"I never make stupid mistakes. Only very, very clever ones." ~ The Doctor

Have you tried to turn off the internet before booting, I lost ifupdown and ceni last time I made a dist-upgrade and got also stuck at "configuring network interfaces" during boot.
When I closed the modem I could log into KDE. Then manually installed the lost packages with dpkg. Got the packages with help from another linuxdistribution on the same machine because no internetconnection in Aptosid due to the lost packages. Now everything OK.